GRANITE AND SANDSTONE JUNCTION— ARRAN. 155 



and standing out in strong relief, be investigated through- 

 out their most minute ramifications. As an interesting cir- 

 cumstance in regard to this junction, we may state, that 

 the granite does not disturb the direction of the strata in 

 any instance. Thus, although they are traversed in every 

 possible manner, still they preserve the same N. and S. di- 

 rection which they had when at a distance from the granite. 

 It is to be particularly noticed also, that the lines of direc- 

 tion, when visible in the imbedded masses, agree with those 

 of the strata. 



At a distance from the granite, the greywacke of this 

 district, exhibits only the usual aspect, but when in contact 

 with it, it affords a different series of characters, and is then 

 generally composed of very minute crystalline grains of 

 white felspar and mica, with a slight intermixture of quartz. 

 It has a perfect granular structure, and exhibits nothing 

 which approaches either to gneiss or mica-slate, but, on the 

 contrary, is only to be considered as a greywacke which has 

 lost its mechanical aspect through the influenceof the granite 

 rocks which rise through it.* The granite of Loch Doon 

 is of two kinds, the one being a compound of red felspar, 

 quartz, and mica, the other of white felspar, quartz, and 

 mica ; hornblende frequently enters into its composition, pro- 

 ducing then a characteristic syenite. The only structure 

 observable is the tabular, but of this even there are no very 

 marked examples. 



IV. Junction of Granite and Sandstone in Arran. 

 The details we have just given, it is needless to say, prove 

 that in Scotland there is a granite formation newer than the 

 transition strata. We shall, however, adduce an instance of 

 true mineralogical granite being also newer than the old 

 red conglomerate. 



• Dr Grierson, in his "Mineralogical Observations in Galloway," 

 describes this altered greywacke as a compact gneiss. 



